Endoscopes are inserted into a body cavity from outside the body to visualize the interior of the body cavity while allowing medical treatment including injection of a fluid medicine in the cavity wall and exposure to laser beams. They recently have attracted greater interest which has encouraged development efforts.
Endoscopes, especially those endoscopes for visualizing the interior of a thin body cavity, typically a blood vessel are of a configuration wherein a bundle of optical fibers for transmitting and receiving light is accommodated in a flexible catheter tube. The catheter tube is inserted into a blood vessel until it reaches a destined site where the light-transmitting fiber (or light guide) projects light from its distal end to an area under observation and the light-receiving fiber (or image fiber) receives the reflected light at the distal end and conducts it to an imaging section where a visual image is provided for observation.
For visual observation of the interior of a blood vessel by means of an endoscope, the blood which obstructs a view to a site under observation must be removed before observation can be done.
However, prior art catheter tubes used in endoscopes have several problems as described below.